diff --git a/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/UniqueFieldValueValidator.php b/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/UniqueFieldValueValidator.php
index 1917c5c..8a4b445 100644
--- a/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/UniqueFieldValueValidator.php
+++ b/core/lib/Drupal/Core/Validation/Plugin/Validation/Constraint/UniqueFieldValueValidator.php
@@ -29,10 +29,14 @@ public function validate($items, Constraint $constraint) {
     $entity_type_id = $entity->getEntityTypeId();
     $id_key = $entity->getEntityType()->getKey('id');
 
+    $values = array();
+    foreach ($items->getIterator() as $item) {
+      $values[] = $item->value;
+    }
     $value_taken = (bool) \Drupal::entityQuery($entity_type_id)
       // The id could be NULL, so we cast it to 0 in that case.
       ->condition($id_key, (int) $items->getEntity()->id(), '<>')
-      ->condition($field_name, $item->value)
+      ->condition($field_name, $values, 'IN')
       ->range(0, 1)
       ->count()
       ->execute();